Question

Out of NaCl and AgCl, which one shows Frenkel defect and why? 

Answer 1

The Frenkel defect is that in which one smaller ion (usually cations) move from its lattice position to an interstitial site i.e. a tetrahedral octahedral hole to form a vacancy in the lattice. Of course, AgCl has the defect because the size of AgCl is intermediate and since the size of Ag⁺ cation is smaller than chloride ion so it can move to interstitial spaces causing Frenkel to defect while in NaCl (alkali metal halide) they have a larger size of cations which do not fit into voids and so the defect is not shown by the alkali metal halides.